This special issue of Pure and Applied Optics is devoted to physical optics
and coherence theory in honour of Professor Emil Wolf, one of the world's most
distinguished scientists in these fields, whose 75th birthday fell on 30 July last
year.
Professor Emil Wolf
Emil Wolf was born and grew up in Prague in Czechoslovakia. Being of Jewish
origin, he fled the country after it was occupied by Nazi Germany in 1939. After
brief periods in Italy and France (where he worked for the Czech government in
exile), he arrived in Great Britain in the summer of 1940. He resumed his education
the following year at the University of Bristol, where he earned a BSc degree in
mathematics in 1945. It was as a postgraduate student that he began his studies in
optics, designing the aspheric corrector [1]. After receiving
a PhD degree from Bristol in 1948, he moved with his thesis supervisor, Dr E H
Linfoot, to Cambridge University as a research assistant at the university
observatory. It was during this period that he made several important contributions
to the diffraction theory of aberrations [2] and to the study
of the structure of optical fields in focal regions, a subject which he still
continues to work on today. Also at that time his association with the exiled
Hungarian scientist Professor Dennis Gabor began. Gabor, who was awarded the 1971
Nobel Prize in Physics for the invention of holography, was then at Imperial
College. With the help of Gabor, Wolf obtained his next position, assistant to Nobel
Laureate Max Born, who was then the Tait Professor of Mathematical Physics at the
University of Edinburgh in Scotland. Born wanted to produce a revised English
translation of his 1933 work Optik, and needed an assistant to help in this
task. However, as the project progressed, the book evolved into an entirely more
comprehensive and authoritative text. Since its publication in 1959 Principles
of Optics by Max Born and Emil Wolf [3], or as it is
more widely known `Born and Wolf', has become one of the most widely cited books in
physical science, having been reprinted 15 times, and at the time of writing, a 7th
edition is under preparation for publication by Cambridge University Press.
Following his years at Edinburgh (1951 - 54), from which university he received a
DSc degree in 1955, Wolf was a research fellow at the University of Manchester (1954
- 59). Here Wolf published his seminal papers on coherence, a subject which he had
begun investigating at Edinburgh. The theory of optical coherence, which had been
largely originated by Fritz Zernike and others, was at that time a rather empirical
series of formulae by which the visibility of interference fringes could be
calculated. Wolf's 1955 paper [4] placed the theory on a firm
theoretical basis, and established that the two-point correlation function 
obeys in free space the pair of wave equations
Also while at Manchester, Wolf worked with Brian Thompson, then a PhD student (who
later became Director of the Institute of Optics and Provost of the University of
Rochester), to produce a well-known experimental paper [5]
which confirmed the calculations of fringe visibilities based on Wolf and Zernicke's
earlier theoretical work.
In 1957 Wolf spent a sabbatical year at New York University, and in 1959 he was
invited by Professor Robert Hopkins, director of the Institute of Optics, to join
the faculty of the University of Rochester in New York State, where he has remained
ever since, except for a year as a Guggenheim fellow at the University of
California, Berkeley (1966 - 67), a year as a visiting Professor at the University
of Toronto (1974 - 75) and a semester as a Distinguished Visiting Professor at the
University of Central Florida (spring 1998). In recognition of his outstanding
accomplishments, he was appointed to the Wilson Chair of Optical Physics at the
University of Rochester in 1987. He has supervised (and continues to supervise)
about 30 PhD students, including the editors of this special issue, many of whom
have made contributions to this special issue, and also continues the regular
academic activities of a full time professor of physics at the University of
Rochester.
Wolf's work at Rochester in coherence theory, a good deal of it in collaboration
with Professor Leonard Mandel, led to a classic review article on the subject in
1965 [6]. This article, which is one of the 100 most cited
articles published by Reviews of Modern Physics since 1955, proved so
popular that the authors decided to expand it into a full length book which finally
appeared in 1995 [7]. His important investigations into
the foundations of radiometry and its connection with coherence theory [8], and into the frequency representation of stationary random
fields [9], led to the discovery of a new mechanism by means
of which the spectrum of radiation can be changed on propagation even in free space.
In particular, spectral lines can be shifted independently of the relative motion of
the source and the observer [10]. This phenomenon, which has
come to be known as `the Wolf effect', and is discussed in some of the articles of
this special issue, may have very profound implications in cosmology. It also has
applications to such fields as optical radiometric standards, communications and
remote sensing (for a recent review of this subject, see [11]).
Other research areas that Professor Wolf has pursued include the reconstruction of
objects from diffracted and scattered light: he published the seminal paper on
diffraction tomography in 1969 [12]. He also continued his
work on focused fields [13,14], and,
with Y Li, gave the first explanation of the focal shift, by which the position of
the focal spot can be displaced towards the focusing lens by diffractive effects [15]. He has also made important contributions to diffraction
theory (for example the theory of the boundary diffraction wave [16]), the theory of non-radiating sources, phase retrieval in inverse
problems and the Ewald - Oseen extinction theorem. Lack of space forbids us from
citing all of his papers (over 280 at last count), so we have confined ourselves to
mentioning a few representative examples of his work.
Professor Wolf has been awarded five honorary doctorates, from the University of
Groningen, Netherlands (1989), from the University of Edinburgh, Scotland (1990),
from Palacky University, Czechoslovakia (1992), from the University of Bristol,
England (1997) and from Laval University, Canada (1997). In addition he is one of
eight lifetime honorary members of the Optical Society of America, of which he
served as president in 1978, and which he helped save from itself when it rather
pointlessly attempted to change its name in 1989. He is also a fellow of the
American Physical Society, the British Institute of Physics and the Franklin
Institute and an honorary member of the Optical Society of India, the Optical
Society of Australia and the Czech Academy of Sciences. He has also been the Editor
since its founding in 1961 of the review series Progress in Optics, which
now consists of 38 volumes, and he has also received many awards for his
contributions, including the Ives Medal, the highest award of the Optical Society of
America.
The subjects covered by the papers in this special issue, like Professor Wolf's
research interests, range over a wide variety of fields. Many of the papers are
written versions of talks presented at the Workshop on Physical Optics and Coherence
Theory, also organized in honour of Professor Wolf, which was held at Long Beach,
California, on 17 October 1997. We have arranged the papers into topical sections,
as follows: coherence theory, the Wolf effect and spatial coherence spectroscopy,
scattering and propagation in turbulent media, propagation in nonlinear media,
propagation in dispersive media, periodicities in propagation, optical signal
processing and the fractional Fourier transform, inverse problems and diffraction
tomography, non-radiating sources, beam propagation and characterization and,
finally, focused optical fields. In the spirit of fairness, the papers are arranged
in these sections in the order in which they were received.
We are sure that we express the sentiments of all our contributors and readers
when we wish Emil many more years of productive research. If there were any articles
which were too late for inclusion in this special issue, we are most willing to
consider them for the special issue we are planning for his 100th birthday in 2022,
provided the article is likely to become of equally lasting value as those of
Professor Wolf!
The editors would like to express their deep appreciation to Professor Mario
Bertolotti, Michele Bouchareine and the editorial staff of the Journal of the
European Optical Society, as well as to Tom Spicer, Elizabeth Martin and the staff
of IOP Publishing for their untiring and highly professional help in preparing this
special issue. This issue could not have been produced without the expert help of
the various anonymous referees who reviewed the manuscripts.
[1] Wolf E and Preddy W S 1947 On the
determination of aspheric profiles Proc. Phys. Soc. 59 704 - 11
[2] Wolf E 1951 The diffraction theory of
aberrations Rep. Prog. Phys. 14 95 - 120
[3] Born M and Wolf E 1959 Principles of
Optics (Oxford: Pergamon); reprinted 1998 6th edition (Cambridge:
Cambridge University Press); Japanese translation 1974 - 75 (Tokyo: Tokai
University Press). There have also been several unauthorized editions and
translations: Russian 1970 (Moscow: Nauka); Chinese 1978 - 81 (Peking: Science);
and various Taiwanese versions.
[4] Wolf E 1955 A macroscopic theory of
interference and diffraction of light from finite sources II. Fields with a
spectral range of arbitrary width Proc. R. Soc. A 230 246 - 65
[5]Thompson B J and Wolf E 1957 Two-beam
interference with partially coherent light J. Opt. Soc. Am. 47 895 - 902
[6]Mandel L and Wolf E 1965 Coherence properties
of optical fields Rev. Mod. Phys. 37 231 - 87
[7]Mandel L and Wolf E 1995 Optical
Coherence and Quantum Optics (Cambridge: Cambridge University Press)
[8]Wolf E 1978 Coherence and radiometry J.
Opt. Soc. Am. 68 6 - 17
[9] Wolf E 1981 New spectral representation of
random sources and of the partially coherent fields that they generate Opt.
Commun. 38 3 - 6
[10] Wolf E 1986 Invariance of the spectrum of
light on propagation Phys. Rev. Lett. 56 1370 - 2 Wolf E 1987 Non-cosmological redshifts of spectral
lines Nature 326 363 - 65
[11] Wolf E and James D F V 1996
Correlation-induced spectral changes Rep. Prog. Phys. 59 771 - 818
[12] Wolf E 1969 Three-dimensional structure
determination of semi-transparent objects from holographic data Opt.
Commun. 1 153 - 6
[13] Boivin A and Wolf E 1965 Electromagnetic
field in the neighborhood of the focus of a coherent beam Phys. Rev. B 138 1561 - 5
[14] Wang W J, Friberg A T and Wolf E 1995
Structure of focused fields in systems of large Fresnel number J. Opt. Soc.
Am. A 12 1947 - 53
[15] Li Y and Wolf E 1984 Three-dimensional
intensity distribution near the focus in systems of different Fresnel numbers J. Opt. Soc. Am. A 1 801 - 8
[16] Miyamoto K and Wolf E 1962 Generalization of
the Maggi - Rubinowicz theory of the boundary diffraction wave, Part I J.
Opt. Soc. Am. 52 615 - 25 Miyamoto K and Wolf E 1962 Generalization of the Maggi
- Rubinowicz theory of the boundary diffraction wave, Part II J. Opt. Soc.
Am. 52 626 - 37
Guest Editors
Ari T Friberg Optics Section, Royal Institute of Technology, S-100 44 Stockholm, Sweden
Daniel F V James Theoretical Division T-4, Mail Stop B-268, Los Alamos National Laboratory, Los
Alamos, NM 87545, USA